Data management systems, such as backup servers and file-servers, are typically designed to be centrally stored, managed, and searched. Such systems are available to a user only when the user is connected to the system. These centralized systems also tend to be expensive systems which need a lot of computational and storage capacity along with high throughput to service the access workload of thousands of remote users.
Security may be an issue for people accessing centralized data. In part, this is an issue because centralized data can contain not only those files appropriate for viewing or manipulation by a particular user, but also files the particular user should not have access to. For example, a centralized data management system may contain files from other users, as well as files at levels of security access above the access level granted to the particular user.
In contrast to centralized systems, data management systems may also be distributed with storage nodes that are disconnected from one another. However, such distributed data storage systems generally do not work well, and require much more storage and computational ability at the end points. These computational requirements can increase rapidly with the number of users being supported by the system.